Getting extra hot water

By Arnie Katz

Q: My son and his family are moving in with us, and we're adding a bedroom and bathroom to accommodate our growing household. One concern I have is that the new bathroom will be so far from the water heater that it will take forever to get hot water there, causing us to waste huge amounts of water while waiting for it to get hot. My brother-in-law says we should get a tankless water heater for the new bathroom. My neighbor says just install a small water heater tank for the new bathroom. A plumber friend suggests a hot water circulation pump. Which option makes the most sense?

A:This is a fairly common problem, with two main questions: 1) Do you have enough hot water to meet the needs of your growing household? 2) Will the hot water get to where it's needed in a reasonable amount of time, with minimal waste?

Figuring out whether you have enough hot water for everyone is not so simple. When there are a lot of people in the house, do you run out of hot water? Do you need to have hot water instantly whenever someone wants it, or can you live with occasionally waiting for 15 or 20 minutes before taking a shower? The trend in recent years has been to have very large water heaters (60, 70, 80 gallons) to make sure you never run out and never have to wait a few minutes. That convenience comes with a price: you're always paying to heat water that you don't need or use.

Builders and plumbers generally recommend large capacity systems, either large tanks or tankless, because most of us will be satisfied customers if we never run out of hot water. Few of us think about how much it's costing us on our electric bill each month for that convenience.

If you decide you don't have enough hot water capacity for the number of people, then either the small tank or tankless water heater in or near the bathroom makes sense. The tankless type typically uses less energy, but it can cause a spike in demand, which can be costly during high-demand periods. Also it's often not nearly as efficient as they claim, especially if you compare it to a high-efficiency, well-insulated new tank water heater. I would get proposals for both, including installation, electric service, running gas lines if you're using gas, etc. Make sure the tankless is big enough to meet your needs. Also, if you have reasonable sun exposure on the roof, this would be good time to consider a solar water heater.

If you have enough hot water, but just need to get it to the remote location quicker, it's worth considering a hot water circulation system. They all work. The big difference is in how much you'll pay to operate it each month.

Three basic types of hot water circulation systems:

Pump that continuously circulates hot water. With this type there's always hot water at the furthest fixture from the water heater and everywhere in between. These cost several hundred dollars a year in electricity to run.

Pump that continuously circulates hot water with a timer. The second type is basically the same as the first, but has a timer you can set so you can shut off the pump while you're not using it. This will reduce the energy costs, but you'll still be paying a couple of hundred dollars a year more than you do now.

Pump on a demand controller. When you want hot water, you simply push a button to turn on the pump. It typically takes just a few seconds to get the hot water to your sink or shower, and then the pump shuts off. This type uses very little electricity since it runs only when you need it, and is the only type that actually reduces your energy bills, since you'll waste much less hot water. As a bonus, your well pump will work less, your septic system might last a bit longer, and you won't feel bad watching all that water go down the drain in the middle of our next drought.

About the Author

Arnie Katz is the former building science consultant for Advanced Energy in Raleigh. advancedenergy.org

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